Security light is attached to electric poles located between buildings or alleys for the purpose of illumination and crime prevention. A flasher is installed in each security light.
A photoelectric control method and an electric control method are widely used to control a flasher of a security light.
The photoelectric control method uses a photodiode (photoelectric transformation device). The photoelectric control method uses a characteristic that a reverse current in P-N junction or contact between a rectifying metal and a semiconductor increases a photovoltaic effect due to illumination of light.
However, when a dark current is generated or it is a cloudy day or a lot of dust accumulates in the photodiode, power may be dissipated and persons may complain.
For these reasons, the photodiode has been replaced with an electric flasher.
The electric control method is designed to memorize a year's sunrise/sunset time of an installation region in a memory of one-chip controller and read month, day and time from a clock chip to turn on/off the light at a corresponding month, day and time.
However, an X-TAL oscillator used in the clock chip is not precise and is sensitive to environment and temperature change. Thus, the light may be turned on/off earlier or later.
In order to solve these problems, time signal is received from a satellite radio and a fixed time is recognized only when a signal is received within two seconds from the time signal. When noise is mis-recognized as the time signal and the set time is out of three or more seconds in the clock chip, the time signal from the satellite radio cannot be received. Accordingly, the time is set incorrectly due to the noise.
In order to solve this problem, a lighting system is disclosed in Korean Patent No. 0461047, filed by the present applicant.
The lighting system using GPS includes: a GPS receiver 10 for receiving GPS satellite signal; a controller 20 for receiving position information and time information from the GPS receiver 10 and calculating a position of the sum, sunrise time and sunset time by substituting the position information and the time information into a calculation equation; an input unit 40 for receiving time difference in the sunrise time and sunset time through an operator's key manipulation; and an output unit 50 for outputting a turn on/off indicating signal and a satellite detection indicating signal at the sunrise time and sunset time, which is calculated by the controller 20.
An overall operation of the lighting system constructed as above will now be described. First, the GPS satellite signal is received through the GPS receiver 10, and the position information and the time information are transmitted to the controller 20 through RS-232C communication interface.
The controller 20 calculates the sunrise time and the sunset time, based on the information received from the GPS receiver 10, by substituting the position of the sun, the sunrise time and the sunset time into the calculation equation. Meanwhile, the controller 20 controls the light to turn on/off according to the calculated sunrise time and sunset time. The controller 20 receives information, such as alternate turn-on based on time zones and latenight turn-off when crops grow based on regions, through the input unit 40, and performs the turn on/off operation.
That is, the GPS satellite signal is received, and the position information and the time information are substituted into the calculation equation to automatically calculate the sunrise time and the sunset time. Accordingly, the light can be automatically turned on/off at the sunrise and the sunset.
Referring to FIG. 2, the GPS receiver 10 includes: a low noise amplifier (LNA) 11 for amplifying RF signal received from a GPS satellite through an antenna ANT; an RF filter 12 for filtering the amplified RF signal; an RF front-end IC 13 for converting an output signal of the RF filter 12 into an IF signal; a baseband processor 14 for down-converting the IF signal into a baseband frequency; and a flash memory 15 for storing information necessary for the system.
In such a lighting system, the GPS receiver, the controller, the input unit and the output unit are separately provided. Therefore, a lot of components are used, resulting in an increase of a manufacturing cost.